Terminal pin assembly



Aug. 15, 1961 c. POWERS TERMINAL PIN ASSEMBLY Filed Aug. 7, 195'? NST , xu A Q ,Q xu WW mw s. l, Q

1N VEN TOR. (ha/[65 Powe/5,

United States Patent O 2,996,599 TERMINAL PIN ASSEMBLY Charles Powers, Eau Claire, Wis., assignor to National Presto Industries, Inc., Eau Claire, Wis., a corporation of Wisconsin Filed Aug. 7, 1957, Ser. No. 676,770 Claims.` (Cl. 219-44) This invention relates to electric heating devices, and more particularly to novel and improved means for effectively sealing the terminal portions thereof against moisture.

Although not limited thereto, the invention has particular usefulness with electrically operated cooking utensils, such as a fry pan, pressure cooker, griddle, sauce pan, Dutch oven or the like, wherein a sheathed heating element is cast, brazed to, or otherwise made an integral part of the bottom or other wall portion of the utensil. It is highly desirable from a point of view of sanitation and general cleanliness that one be able to completely submerge such utensils including the heating element in water so that they may be washed, and without danger that water will seep through the terminal portions or ends of the sheathed element to damage the same.

Thus a principal object of the invention is to provide simple, economical and practical means for obtaining a water-proofed connection between the sheathed heating element and a vpair of terminal connection members through which the heating element is connected to a source of electrical power. -v

A further object of the invention is to provide a tubular sheathed heating element having its opposed ends joined to terminal posts by a water-tight positive electrical connection.

Still another object of the invention is to provide simple uncomplicated and eflicient means of obtaining the desired waterproof connection between the terminal posts and ends of a sheathed heating element while electrically insulating the terminal posts from the sheath and/ or casting or wall of a `device to which the heating element is mounted.

In achieving these and other objects, the invention contemplates that the ends of a heating element will be provided with a threaded portion extending outwardly beyond the extent of the protective sheath for connection with a pair of terminal posts or other terminal fasteners. The inner end of the posts is preferably flanged to provide a relatively wide annular bearing surface; and between said surface and the end of the pr-otective sheath for the heating element, is mounted a ceramic washer having a pair of discs of heat-resistant, resilient material, such as silicone rubber, on either side thereof for effecting a seal between it and the adjacent end surfaces of the sheath and terminal post by tightening of the terminal post on its threaded connection with said protruding portion of the heating element.

One of the features of the invention is that the insulating washer and preferably also the flanged end of the terminal post are specially contrived so that as the terminal post is tightened, the `discs will not only be tightly wedged between the washer and ends of the terminal post and sheath, but the discs will also assume a tortuous shape to increase resistance to moisture penetration between the washer and ends of the terminal post and sheath.

In this connection, it is a further feature of the invention that the ceramic washers are recessed on opposed sides, and that said recesses are controlled in diameter to be slightly in excess of the diameter of the anged end of the terminal post and external diameter of the sheath, the resilient discs being of suiciently larger diameterthat as the terminal posts are tightened, the outer 2,999,599 Patented Aug. 15, 1961 ICC periphery of the discs will be squeezed over and around the adjacent peripheral edge of the ends of the terminal post and sheath to increase the effective seal. Preferably also, the ceramic washer is provided with a bore slightly greater than that of the protruding portion of the heating element which it encircles, so that as the terminal posts are tightened, material of the vdiscs will also be extruded or squeezed into the space between said portion and the wall of the bore in the washer. The bore through the anged end of the terminal may also be similarly enlarged to permit some of the material of the adjacent disc to be squeezed into said space between the protruding portion of the heating element and the terminal post to increase still further the sealing effect of the discs.

Thus, a further object of the invention is to provide novel means and method of eiectively sealing against moisture penetration the connection of the terminal post to the end of a sheathed heating element having an insulating washer ydisposed between the terminal post and the sheath to prevent the conduction of electricity therebetween.

Another object is to provide a novel shape to such an insulating washer by means of which the sealing discs between it and the ends of the sheath and the terminal post may be extruded into shapes and related to the washer, terminal post, heating element and its sheath as to effectively prevent the penetration of moisture into the interior of the sheathed heating element even under circumstances where the heating element is submerged into hot soapy water, as in washing the utensil.

Still another object of the invention is to provide arresting means which will confine and/or limit movement of the sealing discs so that the material thereof will extrude under the tightening of the terminal post on the threaded end of the heating element into all available nooks and crannies or spaces provided purposely or because of imperfections in the adjacent surfaces of the washer, terminal post and sheathed heated element against which they are compressed.

Many other objects as well as advantages and/or features of the invention will be apparent from the description of a preferred embodiment of the invention which follows and when taken in conjunction with the drawing wherein:

FIGURE 1 constitutes a fragmentary View, partly in section, to show the terminals of a sheathed heating element constructed and assembled with the ends thereof in accordance with the invention; the parts of the terminal connection to the left hand side of the figure being in exploded relation to illustrate the parts before being assembled;

FIGURE 2 illustrates diagrammatically how a water droplet might bridge the gap between the terminal pin and the metal of the cooking vessel in a prior art construction to permit a short circuit; and

FIGURE 3 illustrates how the present construction prevents such a short circuit.

Now referring more particularly to the igures, 10, l represents the ends of a sheathed tubular one-piece heating element HE which has been cast, brazed, or otherwise mounted on o1' in the bottom wall of a cooking vessel CV or other device, and which ends 10, 10 of the heating element have been brought into adjacent spaced parallel relation and extended through a mounting portion MP on the bottom wall of said cooking vessel CV adjacent one side thereof to receive and be connected with its Iterminal posts 11, 11 which are disposed in conventional spaced parallel relation whereby they may be conveniently secured by insertion into the receiving receptacles of a connector plug or other means (not shown) to a source of electrical power for purpose of energizing the heating element.

As illustrated by the right hand terminal connection, which is shown in section, it being understood that both terminal connections are identical, heating element HE is indicated as comprising a resistor coil 12 extending lengthwise of its tubular protector sheath 13 which may be made of a variety of materials, but in the particular instance, preferably is of metal. Protruding outwardly of the opposed ends 10, of the heating element are threaded portions 14, 14 which are soldered or otherwise electrically connected to the ends of resistor coil 12. The heating resistor co-il 12 is embedded in a compact mass of electrically insulating and high heat conducting material 15, for example, magnesium oxide, which can be loaded into the sheath 13 in powdered form around the resistor 12 and protruding portions 14, and then cornpacted into a dense mass by means of elongating and reducing the diameter of the sheath 13, usually by swaging or rolling.

Washers 16, 16 of ceramic or other insulating material are disposed over each of the protruding ends 14, 14 of the heating element so as to electrically insulate the terminal posts and prevent their short circuiting through the sheath 13 and/ or the metallic material of the vessel CV. Preferably, recesses as lat R are provided in the mounting portion MP to provide clearance for convenient assemblying of the washers 16 over the ends of the sheathed heating element.

Since it is contemplated that the cooking vessel CV will be completely submerged in hot soapy water for efficient cleansing and washing of the same, it is essential that the protective l-ayer of heat conducting and electrically insulating material be sealed within the sheath 13 against the possibility of water entering through the ends thereof. To effectively provide this seal, sealing discs 1'7 and 18 are provided on opposed sides of the washers 16. As illustrated in the exploded version of the terminal connection to the left hand side of the ligure, discs 17 and 18 are formed with substantially parallel opposed surfaces and may be conveniently cut from, or stamped out, of sheet stock to the required size and shape. Although these discs may be formed of a variety of high heat-resistant, resilient, compressible materials, the reasons for which characteristics will be made more clear hereinafter, I prefer to use discs of silicone rubber which have the softness and resiliency of natural rubber, but, in addition, are equally unatected by high or low temperatures, retaining indefinitely their elasticity and resiliency at temperatures of 300 F. and up to 500 F.

One of the features of the invention is that the ceramic insulating washers 16 are provided with opposed recessed areas 19 and 20 which serve as retaining seats for the discs 17 and 18. Recessed area 19 is preferably made to a diameter slightly in excess of the external diameter of the sheathed end of the heating element 10, but somewhat smaller in diameter than the `disc 17 which is to be seated therein. The recessed area 20 is also preferably dimensioned so as to be somewhat greater in diameter than the diameter `of the adjacent flanged end 21 of the terminal posts 11, and preferably somewhat smaller than the diameter of the disc 18. The central bore Z2 of washer 16 is also made somewhat larger than the diameter of portion 14 over which it is positioned in the assembly to provide an annular free space 23 between its peripheral surface and the wall of said bore 22. The inner bore of each of the terminal posts 11, 11 below the threaded portion thereof is also enlarged at 24 below the threaded end thereof to provide a similar space encircling the terminal or protruding portion 14 of the heating element.

Thus, as the terminal post 11 is tightened on its threaded connection with the portion to obtain its required electrical connection with the heating element HE,

the simultaneous eifect is to also urge the ceramic washer 19 and 20 of washer 16 and against the end surface 25 of the heating element and against flanged end 21 of the terminal post 11, respectively. The tightening of the terminal post on its connection is not complete until the outer peripheral edge of the disc 17 is turned about the end 25 of the heating element, and compressed into intimate sealing relation between the surrounding wall 26 of recess 19 and the adjacent end 10 of the sheathed heating element which ha-s thereby been drawn into recess 19.

Simultaneous therewith, wall 26 of recess 19 and wall 27 of recess 20 serve to restrict and confine outward movement of the material of the said discs 17 and 18 under the tightening action of the terminal post 11 whereby portions of disc 18 are caused to extrude into spaces 23 and 24 to form annular dams 28 and 29 about portion 14 in spaces 23 and 24. Portions of disc 17 are also compressed or forced into space 23 to form. a further annular darn 30 about portion 14 whereby the discs 17 and 18 effectively bar the penetration of moisture between the washer 16 and ends 25 of the heating element 10 or flanged end 21 of the terminal post 11. The sealing effect is, of course, considerably enhanced by the wide bearing surface provided by the flanged end 21 against the disc 18, as well as by the wide bearing contact that end 25 of the heating element 10 affords against disc 17. If desired, means such as grooves 31 may be also provided in the bottom surface of the recessed areas 19 and 20 to aid in retaining the discs 17 and 18 against slippage, and thereby contribute to maximum extrusion of material in areas 28, 29 `and 30.

By reason of the fact that the size of disc 17 is controlled so that a portion 32 thereof is also forced into the space 3B between the marginal ends of the sheath 13 and wall 26 of recess 19 of the washer 16, the sealing effect is further enhanced. One of the unique aspects of the construction is that the material 15 which is to be protected from moisture is itself relied upon at 25 to help in the compressing action on disc 19 to urge its portions 32 and 30 into their damming relation to increase the effectiveness of the sealing function of said disc .19.

A further advantage which results from the aforesaid construction is the protection it laifords against possible grounding of the terminal pins by water droplets allowed to collect about the base of the terminal pin connection. In a construction such as illustrated in FIGURE 2 wherein the ceramic Washer 16A has substantially the same external diameter as that of the terminal pin at 11A, water deposited at W might easily bridge the gap between the terminal pin and vessel to create a short circuit. However, in a construction according to the present invention, the possible path of current leakage to ground is made as long as possible. Not only does the end of theheatin-g element protrude outwardly from the base of recess R in the cooking vessel CV but the ceramic washer 16, by

reason of its opposed recesses 19 and 20= into which the ends of sheath 13 and pin 21` are respectively seated, is cupped thereabout and of suiciently greater diameter as to prevent any such droplets of water (FIGURE 3) formed about the connection from bridging the space between the vessel CV or sheath A13 and the end 21 of the terminal pin.

Although conceivably terminal posts 11 could be directly connected to the respective terminal ends 14 of the heating element by means other than the aforedescribed threaded connection, such a threaded connection is preferable, and has the advantage that it permits careful and positive control of the compressing `action on the discs 17 and 18, so as to assure that the required sealing function will be obtained. This can be accomplished automatically by using a torsion wrench which will apply the necessary torque found to be in the neighborhood of seven inch pounds. Conceivably also, instead of utilizing terminal posts 11 in the form illustrated, locking nuts might be relied upon to obtain the required compression of discs 17 iand 18, and in which instance, the ends of portions 14 extending through the locking nuts Would constitute the terminal posts by which the heating coil is connected to a source of electrical energy.

Thus all the objects and advantages, as well as features of the invention have been described as obtainable in a convenient, simple, practical and economical manner. Furthermore, it will be obvious from said description that many changes and/or modifications may be made within the spirit of the invention as defined in the appended claims, and accordingly, it will be understood that the afore-description is not to be taken in a limiting sense, but merely as illustrative of a preferred embodiment of the invention.

Having described my invention, I claim:

I1. An electric heater comprising a tubular sheath, an electrical resistor within said sheath and having an externally threaded terminal post extending outwardly of an open end of the sheath, insulation packed within said sheath about the resistor and terminal post to flush with the end of the sheath, a resilient heat resistant annular disc about the terminal post and engaging the end surface of the sheath and insulation packed therein, said annular disc having an inner periphery closely engaging the terminal post and an outer periphery of a diameter greater than that of the sheath, a rigid insulating washer having a bore through which said terminal post extends and having a circular recess concentric with said bore including a base overlying the end of the sheath and a sidewall surrounding the exterior side surface of the sheath adjacent its said end, said recess having a diameter larger than that of the end of the sheath which it receives but smaller than that of the disc, and a locking member having an internally threaded bore receiving and threadedly connected to said terminal post, said locking member having a Wide area annular end surface about the terminal post and which uniformly bears against the washer, said locking member being tightly screwed against the rigid washer causing the base and side walls of the recess to confine the resilient heat-resistant disc and compress the same between the said sidewalls and base of the washer and the end of the sheath, the outer peripheral part of said disc extending over the said end of the sheath and forming a continuous darn between the sidewall of the recess and the outer side surface of the sheath adjacent its said end, and the inner peripheral part of said disc extending into the bore of the washer and about the terminal post, Said disc thereby serving to prevent penetration of moisture past the insulating washer and into the interior of the sheath.

2. An electric heater comprising a metal body, a sheathed and insulation packed resistor on said metal body having its ends extending clear of the body and having exteriorly threaded terminal posts extending beyond the ends of the sheath, the insulation being packed level with the ends of the sheath, a connection member threadedlymounted on the end of each said terminal posts, said connection member having a wide area annular bearing surface extending about the terminal, an insulating washer positioned between said end of the sheath and bearing surface of the connection member, said washer having a recess provided with a base and surrounding sidewall to receive the end `of the sheath, and a pair of relatively thin resilient heat-resistant annuli, one on each side of the washer, said connection member being so inwardly drawn on its threaded connection with the terminal post as to compress the two annuli between the washer and the respective ends of the connection member and Sheath into intimate sealing contact therewith, the resilient annulus between the washer and end of the sheath having its outer peripheral margin extruded over and about the adjacent outer peripheral edge of the sheath and between said sheath and Ithe surrounding sidewalls of the recess in said washer, and both annuli having their inner peripheral portions about the terminal postrextruded into the bore of the washer and about the terminal post.

3. An electric heater comprising a tubular sheath, an electrical resistor within said sheath and having an exteriorly threaded terminal post extending outwardly of an open end of the sheath, insulation packed within said sheath about the resistor and terminal post to a substantially iiush level with the end of the sheath, a rigid insulating washer having a central bore through which said terminal post extends and concentric recesses in the upper and lower sides thereof, each of said recesses including a base of diameter greater than the diameter of said sheath and a surrounding sidewall, a resilient heat-resistant sealing annulus on each side of said washer and of an external diameter initially greater than that of the adjacent recess, and a locking member threadedly connected to said terminal post and having a wide area annular bearing surface encircling said terminal post and of a size greater than the sheath and which seats within the upper one of the recesses in the insulating washer, said locking member being tightly screwed against the rigid washer to exert uniformly firm pressure on the resilient heatresistant annuli confined within the respective recesses of the washer, said annuli resiliently filling the space between the base of said recesses and the sheath and bearing surface of the locking member, the outer peripheral marginal portions of said annuli being thereby extruded over and about the sides of the respective sheath and locking member and the inner peripheral marginal portions of said annuli being extruded thereby into the central bore of the washer about the terminal post between the sidewall of the said recesses and the terminal post, said annuli thereby serving to prevent penetration of moisture past the insulating washer and into the interior of the sheath.

4. An electric heater comprising a metal body, a tubular sheath, an electrical resistor within said sheath mounted on said body with ends extending clear thereof and terminating in a pair of terminal posts protruding outwardly of the ends of the sheath, and insulation packed in said sheath about the resistor and its terminal posts to flush with the ends of the said sheath, the outer end of its said terminal posts being exteriorly threaded, said terminal posts each having a first relatively thin annulus of resilient heat resistant material fitting thereabout and covering the end surface of the insulation, a rigid insulating washer having a pair of recesses on its opposite sides each including a base and a sidewall and a centrally located communicating bore through which the terminal post extends, the inwardly disposed one of its recesses receiving said iirst annulus, a second annulus of resilient heat-resistant material fitting about the terminal post and received in the other recess of the insulating washer, and a terminal pin having an internally threaded bore in one end receiving the exteriorly threaded end of the terminal post and threadedly connected thereto, said terminal pin having a flanged part about said bore provided with a flat inner surface dimensioned to be received within said other recess of the washer and to have uniform wide area contact with said second annulus about the terminal post, said terminal pin being sufficiently tightened on the terminal post as to firmly compress the two annuli into the respective receiving recesses of the ceramic washer and said first annulus into intimate contact with the end surface of the insulation, the sidewall and base of said two recesses of the washer confining the material of said respective annuli so that said recesses are essentially cornpletely filled by said annuli and portions of said `annuli extruded into the bore of the washer about the terminal posts to effectively seal said ends of the sheath against possible penetration of moisture to the insulation packed resistor within.

5. An electric heater according to claim 2 wherein the insulating washer comprises a ceramic material and the resilient heat resistant annuli comprise silicone rubber.

(References on following page) UNITED STATES PATENTS McNab July 4, 1933 Lacy June 30, 1936 Smith Nov. 26, 1940 Charbonneau et a1 Nov. 29, 1949 Hasley Nov. 4, 1952, Hasley Nov. 4, 1952 8 Dzaack Ian. 6, 1953 Temple Jan. 13, 19,53 Buggs NOV. 17, 19,53 Charbonneau 'Feb. 5, 1957 King June 24, 1958 Sheahan Nov. 24, 1959 FOREIGN PATENTS 

